Bit sharpener



Oct. 8, 1946e 3201' 2,408,916

BIT SHARPENER Filed Oct. 6, 1944 2 Sheets-Sheet 1 INVENTOR. ANDRE CROT Patented Oct. 8, 1946 2,4Q8,916 BIT SHARPENER Andre Crot, North Hollywood,

Corporation,

Lockheed Aircraft Calif.

Calif, assignor to Burbank,

Application October 6, 1944, Serial No. 557,412

(or. 51-2s2) 4 Claims.

This invention relates to special machine tools for machining helical surfaces of any desired pitch and relates more particularly to and finds its most frequent application to the forming and sharpening of spiral or helical cutting edges of tools such as drills, router bits, milling cutters, and reamers.

Heretofore a manual manipulation of the tool with respect to a grinding stone has been usually employed for the purpose of resurfacing or sharpening spiral or helical cutting edges of drills, router bits, milling cutters, reamers, and the like tools, with the result that such operations were slow and inefficient and resulted in inaccurately shaped, poorly operating tools.

It is an object of this invention to overcome the disadvantages of the manual method and other methods heretofore employed for reconditioning and machining spiral or helical edged tools by providing an automatic machine for this purpose which will be accurate, efiicient and fast in operation.

The objects of this invention are attained in general by a machine capable of imparting, between limits, any desired one of an infinitely variable combination of simultaneous rotation and reciprocation motions to a work piece such as a drill, router bit, or reamer, whereby a cutting or grinding operation may be performed on such workpiece along any corresponding helical edge or path having any desired pitch.

These and other objects and features of novelty will be evident hereinafter in the description which, together with the following drawings, illustrate preferred embodiments of the invention.

Figure 1 is a perspective view of the general arrangement of the apparatus of the invention in operative position.

Figure 2 is an end cross-sectional view taken online 2-2 of Figure 3.

Figure 3 is a cross-sectional side elevation of the machine taken on line 3-3 of Figure 2.

Figure 4 is a cross-sectional detail of the chucking unit carried by the apparatus of Figure 3.

Figure 5 is a cross-sectional View taken on line 5-5 of Figure '2.

Figure 6 is a detail view of the stop plate taken on line 6-6 of Figure 3.

Referring now to the drawings in which like reference characters refer to corresponding parts throughout the several figures, the apparatus of the invention is as follows:

A housing In is provided for enclosing the major elements of the machine, said housing having a removable top i I normally held in place by means of a pair of machine screws i2 and I3.

Extending lengthwise through the upper portion of the housing is a composite shaft comprising tubular spindle M and a coaxially positioned spindle drive shaft l5, said tubular Sl dle and spindle drive shaft being constructed to snugly telescope to provide for limited axial reciprocation with respect to one another and common rotation together. Common rotation of the spindle drive shaft I5 and the tubular spindle I4 is effected by means of a pair of keys it retained in suitable recesses on the inside surface of the tubular spindle and adapted to slide axially within a pair of elongated key-ways l7 formed in the surface of the drive shaft IS.

The tubular spindle I4 is reciprocatably and rotatably supported in a bushing l8 which is in turn retained within a bearing support or bearing holder 19 which is inserted and suitably bolted in place, as shown at 20 in an opening 2| located through the wall of the forward end of the housing In.

As best shown in Figures 3 and 4 the tubular spindle is provided with a flange 22 on its outer end to which may be bolted a chuck body as shown at 23. Any suitable chucking means may be employed depending upon the type of workpiece or tool to be machined but for convenience of illustration herein a split collet type of chuck is shown and described. A split collet grip-assembly providing a plurality of radially positioned jaws is retained as a unit within the collet body by means of an inwardly projected unitary shank 25. A nut 26 having an inner tapered face is shown at 2! and serves upon tightening upon threads 28 of the chuck body to wedge the collet jaws 2 l into gripping position upon the cylindrical shank 29 of the tool to be machined.

The inner end of the tubular spindle l4 within the housing If! carries a thrust bearing iii] which comprises an inner cylindrical race 3! and outer cylindrical race 32 and intermediate needle bearings as shown at 33. At either end of the inner and outer races 31 and 32 thrust washers as shown at 34 and 35 are provided which abut at one end against a collar 36 formed integral with the spindle and at the other end against an adjustable stop nut 31 which is in turn carried on the inner threaded end of the tubular spindle. A look nut 38 is provided for retaining. the thrust nut 31 in adjustment.

The spindle drive shaft [5 which telescopes into the bore of the spindle M is rotatably supported in a bushing Ml which is retained in a suitable opening in the end of the housing iii in coaxial alignment with respect to the beiorementioned bearing holder l9 and bushing l8. As hereinbefore stated the drive shaft [5 is of such a size as to make a snug slidin fit within the bore M of the tubular spindle I4, whereby said tubular spindle may be reciprocated With respect to said drive shaft through bushing iii. .A spur gear 48 is keyed at 42 to the drive shaft I 5 adjacent the inner surface of the rear end of the housing. A hub member 43 is keyed at 44 and retained in adjusted axial position on the outer exposed end of the drive shaft I5 by means of a set screw 45. The inner flared end 48 of the bushing 40 acting against the hub of the gear 8 and the washer 41 acting intermediate the housing and the adjacent surface of the hub 53 serves to restrain the spindle drive shaft against axial movement with respect to the housing.

. An operating lever or handle 50 extends radially from the hub 43, said handle comprising an inner shaft 5I and an outer axially movable tubular slide 52. The inner handle shaft 5I is fixed in radially extending position with respect to the hub 43 by means of threads and lock-nut as shown at 53 and 54 respectively.

The tubular handle slide 52 is slidable or reciprocatable upon the handle shaft 5| within the limits set by the stop nut 64 against the force of the helical spring 55. The helical spring 55 acting under compression normally retains the tubular handle shaft in a maximum outward position against the stop nut 64 on the end of the handle shaft whereby an offset latch member 56 carried at the lower end thereof and movable radially in a slot 56' in the hub 43 will normally be retained in locked position within a radial locking groove 63 which is formed in the rim 5! of a circular stop plate 58 which is in turn adjustably supported from the outer face of the rear end of the housing by means of a pair of suitable machine screw as shown at 58 and 50. A pair of semi-circular slots 61 and 82 as best shown in Figure 6 provide for angular adjustment of the stop plate for suitable angular positioning of the lock groove 63 as desired.

Enclosed within the lower portion of the housing I is a lead screw shaft 65 rotatably supported with its axis parallel with the axes of the before described tubular spindle and drive shaft, in bushings 66 and 61 which are in turn retained in the walls of the housin by means of the bearing holders 63 and 69. A spur gear 10 meshing with the beforementioned drive shaft spur gear 48 is keyed to the lead screw shaft as shown at H and adjustable to a limited degree axially thereon by means of a set screw 72. A collar or abutment 13 is formed integrally with the lead screw shaft and axial motion or play of the lead screw and the lead screw shaft 55 is limited by the abutment of the said collar 13 against the inner flared end 14 of the forward bushing 66 and the contact of the hub of the spur gear 10 with the inner surface of the inner flared end 15 of the rear bushing 61.

The lead screw shaft 65 carries at an intermediate section and formed integral therewith a ground and polished lead screw having a plurality of threads of suitable pitch as shown at l6. A nut 00 having internal threads is threaded on the lead screw '26 and is adapted to axial movement upon rotation of the lead screw shaft 65 as hereinafter more fully described. As an example, a %6, 60 stub tooth lead screw having a major diameter of approximately .875 inch, a minor diameter of .724 inch, a pitch diameter of approximately .80 inch, and a lead of T 5 inch was satisfactorily employed in a machine of the type illustrated. The mating nut 80 is provided with an upwardly extending elongated guide tongue 8I. The guide tongueSI is solidly fixed within a slot 82 formed in the upper side of the said nut 80 and is held therein by means of three countersunk machine screws as shown at 83. The upper, elongated portion of the guide tongue enters and makes an axially sliding fit within a corresponding slot as shown at 04 formed in the lower surface of the housing or outer race 32 of the needle thrust bearing 30. The nut and the needle bearing housing 32 are thus secured against rotation.

The lead screw nut 80 is provided with a pair of coaxial oppositely extending trunnions as best shown at and 86 in Figure 2 and the needle thrust bearing housing 32 is similarly provided with a pair of coaxial oppositely extending trunnions as shown at 81 and 88. The trunnions 85 and 86 of the lead screw nut are each pivotally carried in square cross-head members I9 and 88 and the trunnions 81 and 88 of the needle thrust bearing housing 32 are similarly pivotally carried in square cross-head members 90 and BI.

A pair of oppositely positioned walking beam members 92 and 93 are pivotally supported at a point intermediate their ends by means of a pair of pins or bolts as shown at 95 and 96 which are in turn carried in the inwardly extending ends of a pair of adjustable supporting arms 91 and 98. Each of the walking beams is provided with a pair of elongated slots or slides as best shown at I00 and IOI in Figure 5. The inner longitudinal surfaces of the slots I00 and If serve as guides in which during the operation cross-head members 90-9I and 19-89 slide.

The arms 9! and 98 are movably supported upon a cross-shaft I02 to which they are keyed as shown at I03. The cross-shaft I02 is pivotally supported in a pair of oppositely positioned bushings I05 and I06 located within the side walls of the housing. The cross-shaft I02 is adapted to be adjustably rotated by means of a lever I01 which carries at its outer end a pointer I08 adapted to move over a graduated scale I09 carried on a scale plate H0. The adjustment lever I0"! is adapted to be firmly retained in a given adjusted position with respect to the scale I 09 by means of a knurled nob III the shaft of which extends through the outer end portion of the lever as shown at II 2, and makes threaded connection with a threaded nut which moves in an arc in an internal arcuate recess II3 formed on the inside face of the scale plate H0.

Angular displacement of the adjustment lever I0 1 serves to move the adjustment arm 91 through a corresponding angle which in turn, acting through the pins or bolts 95 and 96, serves to shift the walking beam 92 longitudinally with respect to the cross-heads 19-89, 909l.

A flexible leather boot II5 fixed to the spindle flange 22 by means of a clamping wire I I6 and retained in rotatable fit in an annular groove II! in the outer end of the bearing holder I9 by means of a snap ring H8 serves to prevent foreign matter from entering the bearing surfaces between the spindle shaft I 4 and the bushing l8 which at the same time provides for rotational and reciprocative freedom of the spindle shaft with respect to the apparatus housing I0.

The operation of the apparatus is as follows:

The drill reamer, router-bit, or the like tool which it is desired to sharpen, is inserted into the collet chuck as best shown in Figures 1 and 4. The rotating cutting wheel I20 powered by suitable means such as an electric motor, not shown, is adjusted into position where, for example as illustrated in Figure 1, a router bit is to be sharpened, the cutting edge IZI will make proper contact at the proper angle with the cutter blade I 22. The lever I0I is then adjusted to raise or lower the position of the walking beams 92 and 93 so as to vary the length of the lever arms L1 and La 7 thus imparted to the walking beams 92 and 93 between the pivotal center of the walking beam supports 95 and st and the centers of the crossheads efi-9i at the spindle thrust bearing and cross-heads l9 and 89 at the lead screw nut so that the cutter will, in effect, follow exactly the spiral or helix described by the cutter blade I22. The ratio of the axial motion of the tubular spindle with respect to the axial movement of the lead screw nut will always be proportional to the ratio of the length of the lever arm L1 to the length of the lever arm L2. Axial motion of the spindle it and the chuck carried thereon is thus efiected by means of the opposite axial motion of the lead screw nut til, acting through the two oppositely positioned walking beams 92 and 93. Adjustment of the height or vertical position of the walking beam by angular adjustment of the arm 9'! is thus obviously effective to vary the ratio of the motion of the spindle with respect to the motion of the lead screw nut between certain limits determined by the dimensions of the elements of the machine, particularly the walking beams s2 and 93.

Upon rotation of the spindle drive shaft l5 by means of the handle 52, the lead screw shaft 55 will also be rotated in an opposite direction through the action of the mutually meshing spur gears t8 and Hi. Accordingly, if the handle 52 is rotated clockwise, the drive shaft it: will likewise be rotated clockwise and the lead screw shaft 85 will be simultaneously rotated counterclockwise at a speed which is proportional to the ratio of the number of teeth on the spur gear 68 to the number of teeth on the spur gear '38. Rotation lead screw shaft 65 and the lead screw 56 formed thereon will simultaneously result in axial motion of the lead screw nut 89 to the left as viewed in Figure 3. The motion thus imparted from the nut 86! to the crossheads i9 and 89 contained within the lower slot ID! of the walking beams 92 and 93 will result in counter-clockwise angular displacement of the said walking beams about the centers of their supporting pins 9'5 and 93 with resultant axial motion of the cross-heads so and 91 to the right, as viewed in Figures 3 and 5. Corresponding axial displacement of the spindle thrust bearing to the left will result in an outward extension of the tubular spindle shaft i i. The spindle shaft will thus have imparted to it a simultaneous clockwise rotation and axial translation, the relationship of one to the other of which will depend upon the beforementioned gear ratios between the gears iii and IE1 and the ratios of the lever arms L1 and L2. By computation or by experiment, proper adjustment of the adjustment arm 9? and the corresponding position of the lever it? may be determined for any given relationship between the angular rotation of the spindle shaft and its simultaneous axial motion. Thus any desired motion of the tool to be machined corresponding to any desired pitch or spiral can be obtained. When such relationship has been computed or otherwise determined, the plate I I0 may be calibrated by the placing thereon of a corresponding scale as shown at I09, whereby pre-adjustrnents of the machine may be readily made by simply setting the pointer Hi8 upon the proper marking of the dial I69.

As hereinbeforementioned, the lever arm 50 is normally locked in fixed position against rotaformed by the said 'and said shaft together for simultaneous tion by means of the latch tongue 56 extending into the locking groove 63 formed radially in the circular rim 5'! of the stop plate. Upon depressing the handle slide 52 radially inward against the force of the spring 55, the latch tongue 56 is carried inwardly out of engagement with the groove 63, thus freeing the handle for rotation of the spindle drive shaft iii. In operations where a larger number of the same kind of tool is to be machined or ground, it may be desirable to adjust the angular position of the stop plate by means of the screws 59 and E9 to provide for identical and suitable initial settings of the machine in accordance with the working requirements.

While a grinding wheel, for purposes of illustration, has been shown at I20 in Figure 1, other types of cutting tools may obviously be employed to perform similar operations.

While a preferred embodiment of the invention has been illustrated and described hereinbefore, the invention is not to be limited thereby, but is intended to cover any variation or modification Which falls within the scope of the claims.

I claim:

1. Apparatus for machining a helical surface comprising chucking means for a workpiece to be machined, a coaxial shaft rotatably and axially reciprocatably supporting said chucking means, a lead screw positioned parallel to and adjacent said shaft, drive means coupling said lead screw rotation at a fixed ratio, a nut on said screw axiall movable in response to rotation of said lead screw, a thrust bearing associated with and adapted to move said chucking means axially, a walking beam pivotally coupled adjacent one end to said nut and adjacent the opposite end to said thrust bearing, means to support pivotally said walking beam for angular displacement in response to axial motion of said nut whereby said thrust bearing and said nut are thus coupled together through said walking beam for simultaneous axial motions.

2. Apparatus for machining a helical surface comprising chucking means for a workpiece to be machined, a coaxial shaft rotatably and axially reciprocatably supporting said chucking means, a lead screw positioned parallel to and adjacent said shaft, drive means coupling said lead screw and said shaft together for simultaneous rotation at a fixed ratio, a nut on said screw axially movable in response to rotation of said lead screw, a thrust bearing associated with and adapted to move said chucking means axially, a walking beam pivotally coupled at one point thereon to said nut and at another point thereon to said thrust bearing, means to support pivotally said walking beam for angular displacement in response to axial motion of said nut whereby said thrust bearing and said nut are thus coupled together through said walking beam for simultaneous axial displacement.

3. Apparatus in accordance with claim 1 in which said pivotal walking beam support is adjustable in position with respect to said pivotal coupling to said nut and said thrust bearing.

l. Apparatus according to claim 2 in which said pivotal walking beam support is adjustable in position with respect to said pivotal coupling to said nut and said thrust bearing,

ANDRE CROT. 

